In the on-board electrical system of motor vehicles, the electrical loads are grouped in various classes. There are loads that are absolutely necessary for safe operation and the safety of the vehicle, such as the running lights, engine or other control units, fuel pumps, and so forth. These loads will hereinafter be called xe2x80x9cnon-controllable loadsxe2x80x9d (NSVs).
There are also electrical loads where the driver notices immediately or very quickly that they are turned on or off, such as a passenger compartment fan, radio, seat adjuster, windshield defroster, and so forth. These loads will hereinafter be called xe2x80x9cconditionally controllable loadsxe2x80x9d (BSV).
Finally, there are loads that have storage behavior, so that an interruption in the supply of energy or the turning off of the voltage supplying them is not noticed until after a certain period of time. Examples of such loads are a seat heater, rear window defroster, electric supplementary heaters, the cigarette lighter, and so forth. These loads will be called xe2x80x9ccontrollable loadsxe2x80x9d (SVs). The goal of an energy management system (EM) is to switch the controllable loads, and under certain conditions the conditionally controllable loads BSVs, in such a way that the battery state is or becomes favorable. In addition, with the aid of the energy management (EM), better coupling of the drive train and on-board electrical system should be possible, for instance in order to achieve such functions as drive train relief by deexcitation of the generator during acceleration, or an additionally operative drive train loading during braking by full excitation of the generator.
From German. Patent Disclosure DE-OS 39 36 638, a method is already known in which the loads in a vehicle on-board electrical system are turned off or switched back if a certain load state of the vehicle battery is undershot, so as to prevent the battery from discharging too much. Which load or loads is or will be turned off depends on what group of loads it belongs to. One such group is composed for instance of xe2x80x9cconditionally switchable loadsxe2x80x9d (BSVs) and/or xe2x80x9cswitchable loadsxe2x80x9d (SVs). The group is always turned off completely or reduced in terms of consumption. Several groups that contain xe2x80x9cBSVsxe2x80x9d and/or xe2x80x9cSVsxe2x80x9d are defined. Each group has a priority pertaining to vehicle safety or to the importance of the group. Turning off or resetting of the individual groups begins with the group having the lowest priority. If this does not improve the charge state of the battery, then further groups are turned off or switched back, until the battery load state reaches a certain level.
In addition, from European Patent Disclosure EP 0 601 300 B1, a method is known in which the resetting or turning off of the electric loads in an on-board vehicle electrical system is dependent on the driving state. The driving states pertain to the vehicle speed and stopping on the one hand and the operating state of the internal combustion engine on the other. On the basis of the signals are information furnished by sensors, a control unit of the vehicle can depend, depending on the vehicle state involved, which types of loads should be turned off or switched back either individually or in groups, simultaneously or in succession in accordance with a predetermined order.
In the above-described methods, only energy economy and maintaining operating and vehicle safety are taken into account. The perceptibility of the operating states, such as a decrease in heating output of the seat heater or other loads to be turned off or reset, is not taken into account since the loads are switched in accordance with a predetermined strategy that is invariable, rather than in accordance with their state.
The object of the invention is to adapt the switching strategy or prioritizing of the loads even during operation in such a way that the perceptibility of the operating states caused by the switchover is jointly taken into account, and the ndividual adaptation to specifiable criteria is effected, thus overcoming the disadvantages of the prior art. This object is attained by a method of the invention.
The method according to the invention has the advantage that the effects on comfort that can be caused under certain operating conditions by the energy management are reduced or suppressed entirely in terms of being perceptible and thus are not noticed by the vehicle passengers.
This advantage is attained by performing dynamic prioritizing of the load power; that is, a change in priority can optionally be done under certain circumstances even during operation. By measuring or estimating the operating states of the loads, the loads are assigned priorities as a function of the operating state. In accordance with these priorities, initially only loads of the xe2x80x9cswitchable loadxe2x80x9d priority are switched, and only until the power deficit is compensated for. Only if that no longer suffices are loads of the xe2x80x9cconditionally switchable loadxe2x80x9d class switched (turned off). This assures that the switching of the loads remains unnoticed (neutral in terms of comfort) by the passengers for as long as possible.
Further advantages of the invention are attained by the provisions recited in the dependent claims. These provisions make it possible for instance for individual loads to change their assigned classes, and this change is advantageously made as a function of time and/or of detected operating states. It is especially advantageous that individual loads can be equipped with a certain intelligence that makes it possible for them to assign themselves to the appropriate class, as a function of their operating state.
The prioritizing of the electric loads can advantageously be done vehicle- and/or person-specifically. Aspects of the future driving cycle can be taken into account and the energy management strategy thus influenced. In suitable equipped vehicles with a navigation system, the information provided by it can also be taken into account in setting the switching priorities. With the aid of learning systems (memory functions), the driver can be recognized and the individual driving behavior or individual load activation or comfort preferences of the particular driver can be ascertained and stored in memory and taken into account on future trips, especially in recurring driving cycles.
The energy management extends advantageously not merely to switching electric loads but also includes mechanical components that can be turned on or off in order to achieve a desired effect, such as rpm adaptation or load optimization. The energy management is advantageously performed by means of a control unit, such as an on-board electrical system control unit.